Cahokia: The Great American City That Vanished Before Columbus

Most Americans have never heard its name, which is its own kind of mystery. A thousand years ago, across the river from what is now St. Louis, there stood a city bigger than London at the time, home to tens of thousands of people, dominated by an earthen pyramid larger at its base than the Great Pyramid of Giza. It had suburbs, plazas, astronomical monuments and a complex society. Then, over a couple of centuries, its people left, and the great city fell silent long before any European set eyes on the continent.

Cahokia is the largest pre-Columbian city north of Mexico, and both its rise and its disappearance are only partly understood.

A metropolis of earth

Cahokia flourished from roughly 1050 to 1350 in the Mississippi floodplain. At its peak it may have held twenty thousand people or more, a staggering number for North America at the time, comparable to the largest European cities of the era. Its builders raised more than a hundred earthen mounds, the greatest being Monks Mound, a terraced platform rising a hundred feet with a footprint larger than that of Egypt's largest pyramid, topped by a great building where the city's leaders presided.

They tracked the sky with precision. A ring of tall wooden posts, nicknamed "Woodhenge," marked the solstices and equinoxes against the horizon, aligning the city's ceremonies with the turning year. This was a planned, sophisticated society with social hierarchy, long-distance trade, specialized crafts and a shared religious life, built entirely without the wheel, without draft animals, and without writing.

The darker finds, and the vanishing

Cahokia was not a gentle utopia. Excavation of one mound revealed mass burials, including the sacrifice of dozens of young women interred together, evidence of a society with rulers powerful enough to command death as ritual. That grimness is part of the honest picture.

The central mystery is the ending. Beginning in the 1200s, Cahokia declined, and by around 1350 it was largely abandoned, its people dispersed. No single cause is proven. Leading explanations include environmental strain, deforestation and flooding from the very earthworks and farming that sustained the city, prolonged drought, resource depletion, political or social breakdown, and possibly disease or warfare. It is worth being plain that this was not a lost race or an alien project; it was an Indigenous American civilization that rose, thrived and dissolved for reasons we are still reconstructing.

The residue on the floodplain

Archaeology has recovered the shape of Cahokia, its mounds, its Woodhenge, its trade, its sacrifices, without fully answering why it emptied. Visitors climbing Monks Mound describe the strangeness of standing atop a forgotten metropolis in the middle of America, a whole civilization that history books skip. Evidence explains much. A residue, the unanswered why of the abandonment and the near-erasure from popular memory, does not tidy away, and that is what our readers argue over.

Below, readers have filed their own experiences at Cahokia and other abandoned places that seem to remember their people, each voted True, Fake or Not sure by the jury. Read them and cast your verdict.